1. Field of the Invention
This invention relates to a coaxial line-to-microstrip line transition device for a microwave down-converter used for microwave systems such as satellite broadcasting systems.
2. Description of the Prior Art
Generally, a transmission line used for the microwave device includes as basic elements a wave guide, a coaxial line and, a microstrip line. In a case of connecting different kinds of transmission lines, since the frequency in operation is high, it is important to ensure the earth-connection between the connected lines. Especially the earth-connection between a coaxial line and a microstrip line is difficult due to the completely different line structures. Conventionally, a connector fixed to a package which mounts therein the microstrip line circuit has been used, but it is expensive and unsuitable to mass production.
FIG. 1 is a perspective view of the principal portion of a typical conventional coaxial line-to-microstrip line connector, in which reference numeral 1 designates a coaxial line-to-microstrip line transition connector, reference numeral 2 designates a dielectric substrate provided at the back surface with an earth metal layer 21, reference numeral 3 designates a chassis, reference numeral 4 designates a microstrip line, and reference numeral 5 designate a transistor. On the front surface of dielectric substrate 2 is constituted a microwave circuit comprising the microstrip line 4 and transistor 5 or the like. The dielectric substrate 2 is placed on the chassis 3 so that the earth metal layer 21 is electrically connected with the chassis 3. The inner conductor of the coaxial line-to-microstrip line transition connector 1 and the microstrip line 4 are electrically connected with each other, and the outer conductor of the transition connector 1 is electrically connected with the chassis 3. This conventional coaxial line-to-microstrip line transition connector has good performance with respect to its electrical transition characteristic, but is defective in its high manufacturing cost and unsuitability to mass production.